The Potential of Shea Nut Shells in Phytoremediation of Heavy Metals in Contaminated Soil Using Lettuce (Lactuca sativa) as a Test Crop

Abstract

Contamination of soil and water by heavy metals cause serious risks to living organisms especially humans and the ecosystem in general through direct contact, inhalation and dermal contact. In this study, shea nut shells were used as adsorbent for heavy metals from contaminated soil. Shea tree (Vitellaria paradoxa) is one of the economic tree crops prevalent in Northern Ghana. Leafy vegetables depend on water for their growth and survival and have massive potential of accumulating heavy metals in their edible parts. Accumulation of heavy metals in leafy vegetables makes them dangerous to human health when consumed. It is within this perspective, which made it imperative for the application of shea nut shells to remove heavy metals such as manganese, iron, zinc and copper from contaminated soil with lettuce (Lactuca sativa) as a test crop. Plastic pots filled with soil from Nyankpala with drainage holes at the bottom and contaminated water from Zoomlion landfill site at Gbelahi in Northern Region of Ghana was used. Atomic Absorption Spectrophotometer was used to determine manganese, iron, zinc and copper in the test crop (lettuce). The mean concentration of heavy metals after 21 and 42 days of transplanting were; Fe (271.135 mg/kg and 457.791 mg/kg), Mn (45.245 mg/kg and 77.211 mg/kg) and Zn (20.049 mg/kg and 50.108 mg/ kg). The concentration of copper was below the level of 0.001 mg/kg. According to the results obtained from this research, shea nut shells have the potentials of adsorption of heavy metals from contaminated soil and water hence it is recommended as suitable means of phytoremediation.